This invention relates to a controller integrated with apparatus for the purpose of controlling the operational parameters of the apparatus, and more particularly, to control circuitry operated by processors for a closed loop, self-remedial system. A particular application of the present invention relates to molds utilized with a plastic mold apparatus, such as a hot runner injection mold apparatus.
In the injection mold industry, it is known to have an injection mold apparatus having from one to two hundred plus molding stations. Molds having ninety-six stations are common. Each station is equipped with the functional elements necessary for carrying out the molding process, including a mold cavity, resin feed equipment, and heaters and chilling fluid channels for maintaining resin and the mold in a proper molding condition. In a typical injection mold process, the following steps sequentially take place: (1) the mold cavity closes; (2) molten resin is injected into the closed mold; (3) once the injected resin hardens, the mold is opened; and (4) a formed part is ejected from the opened mold. Each mold cavity can undergo changes in spacing as a result of repeated opening and closing as each finished molded component is ejected. It is critical that the mold return to its precise spacing after the components are ejected and the mold is readied for the next batch. Moreover, in molding components, it is critical to maintain the temperature of the resin within a few degrees of its desired melt temperature in order to achieve the proper quality of the molded components. Given the high production rate of injection molding apparatus, almost instantaneous recognition that the system is out of temperature control is needed.
Conditions in the mold that are important in terms of product quality are the resin temperature, the mold temperature, and mold pressure. If these conditions are out of set ranges, the quality of the final molded components can be adversely affected. For example the molded components can emerge with extraneous plastic along the edges, which is known as “flash”.
Other problems incurred with molding parts are variation and inconsistency in the weight and quality of the components.
Conventional techniques for controlling operational parameters of a mold to maintain the parameters within a range of acceptable reference parameters involves monitoring the various parameters with sensors. The data detected by the sensors is transmitted as analog signals to a controller. Certain examples of the prior art are U.S. Pat. No. 5,551,857, issued Sep. 3, 1996, to Osami Fujioka, which discloses controls for a molding apparatus 39 (FIG. 1); and U.S. Pat. No. 5,795,511, issued Aug. 18, 1998, to Peter G. Kalantzis, which discloses a memory function in FIG. 2 for the operational parameters of the hot side 24 of an injection molding machine.
Some of the disadvantages of prior art techniques for monitoring and controlling the operational parameters of a mold apparatus are attributable to the use of large, stand alone controllers, external to the mold. These controllers are expensive, and require large kilowatt power sources and large heavy cables for connection. The cables that provide the kilowatt power generates resistance in the cables and produces unwanted noise that can result in inaccurate signals from the various sensors. Moreover, a large number of connectors need to be made to connect the mold controller to (i) the mold, (ii) the injection mold apparatus, and (iii) a power source. Effecting these connections delays start-up of the equipment, and can contribute to high labor costs for production of molded parts.
In view of the disadvantages of prior art techniques, there is a need for control apparatus, such as for an injection mold apparatus, and methods for operating the apparatus, that permit accurate, automatic and inexpensive control of operational parameters while minimizing production of defective parts.